The present invention relates to filtration of fluid flow in tubular bodily organs, such as arterial and venous bloodstreams and the urinary tract, and particularly to a filter device for use during angioplasty and atherectomy procedures for relief of stenoses.
Occlusion of arteries by deposition of plaque or by thrombosis ultimately results in lack of sufficient blood flow to tissues served by the occluded artery, and eventually may result in necrosis. Patency of the lumen of an artery may be restored by different procedures including angioplasty and atherectomy, but these procedures may dislodge pieces of plaque or blood clots large enough to cause dangerous occlusion of smaller downstream vessels.
It is important not to have pieces of material such as plaque or blood clots significantly larger than blood cells moving freely in circulation in the blood vessels because of the danger of such particles lodging in a location which would interrupt the blood circulation to critical tissues such as heart muscle, brain tissue, etc.
Procedures in which foreign objects such as catheters are introduced into blood vessels may result in the formation of clots which might ultimately be released into the bloodstream. It is thus important in such procedures to prevent movement of dislodged blood clots or plaque and the like, and to capture and retrieve such pieces of material from within the blood vessel as a part of the completion of such procedures.
Various devices are known for the purpose of cutting or abrading plaque material from the interior lining of arteries. Their use has usually been accompanied by the need to prevent blood flow during the procedure, as by the use of a balloon-tipped catheter completely occluding an artery at a position downstream from a stenosis being treated by the procedure, in order to retain pieces of plaque freed from the arterial wall. However, balloon-tipped catheters do not always work satisfactorily to retrieve debris. They may squeeze pieces of plaque against an arterial wall, resulting in loose temporary adhesion and subsequent release into the blood stream. Additionally, use of a balloon-tipped catheter is necessarily of limited duration because of the resulting lack of blood circulation to tissues normally fed by the artery on which the procedure is being performed.
Various implantable filter devices are known for use in large veins, to trap blood clots and thus prevent them from being circulated into the heart, lungs and other bodily tissues where blood vessel blockage could be disabling or fatal. Such implantable blood filter devices, however, are not well adapted for use in connection with angioplasty or atherotomy, because the implantable devices are not easily removable. Additionally, such implantable devices are not likely to stop smaller pieces of material which might nevertheless be carried through the bloodstream to cause dangerous blockage of small arteries or capillaries. Such devices are disclosed, for example, in Mobin-Uddin U.S. Pat. Nos. 3,540,431 and 4,727,873, Kimmell, Jr. U.S. Pat. No. 3,952,747, Simon U.S. Pat. No. 4,425,908, Gianturco U.S. Pat. No. 4,494,531, Molgaard-Nielsen et al. U.S. Pat. No. 4,619,246, Metals U.S. Pat. No. 4,688,533, Palmaz U.S. Pat. No. 4,793,348, and Palestrant U.S. Pat. No. 4,832,055.
One filter-like device for use in connection with removal of plaque from within an artery is disclosed in Wholey et al., U.S. Pat. No. 4,723,549, but the process of withdrawing the device appears likely to release particles of plaque into the bloodstream, and the device appears likely to allow flow of unfiltered blood when it is located in a portion of a blood vessel with an irregularly or asymmetrically shaped lumen.
Clark, III, U.S. Pat. No. 3,996,938 discloses a cylindrical mesh tube with its opposite ends attached respectively to a tube and a central wire within the tube, so that relative movement of the wire and tube results in radial expansion and longitudinal contraction of the mesh material. The mesh material acts as a filter in order to remove a blood clot from within a blood vessel.
Luther U.S. Pat. No. 4,650,466 discloses a device somewhat similar to that shown in the Clark, III, patent but intended to be used for abrading plaque from an arterial wall and not to filter blood.
What is needed, then, is a device able to prevent downstream transport of materials significantly larger than blood cells, as well as a method for its use to permit the flow of blood to continue during a procedure, such as angioplasty or atherectomy to correct a stenotic condition in a blood vessel. Such a device preferably should be able to capture debris and permit retrieval of the debris without pieces of debris being released into the bloodstream, either during use or as a result of retrieval. Additionally, the device should be able to be configured small enough to pass a stenosis in an artery, yet be dependably expandable, to peripherally coapt completely with an irregular vessel wall, to fill the lumen of the artery at a location downstream from a stenosis, so that the entire bloodstream through the artery is filtered. Such a device also needs to be effective at a location where a branch diverts from the main stem of blood vessel at a location downstream of a stenosis being treated.